/* LRW: as defined by Cyril Guyot in
   *	http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
   *
   * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
   *
   * Based om ecb.c
   * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   */
  /* This implementation is checked against the test vectors in the above
   * document and by a test vector provided by Ken Buchanan at
   * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
   *
   * The test vectors are included in the testing module tcrypt.[ch] */
  #include <crypto/algapi.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/scatterlist.h>
  #include <linux/slab.h>
  
  #include <crypto/b128ops.h>
  #include <crypto/gf128mul.h>
  
  struct priv {
  	struct crypto_cipher *child;
  	/* optimizes multiplying a random (non incrementing, as at the
  	 * start of a new sector) value with key2, we could also have
  	 * used 4k optimization tables or no optimization at all. In the
  	 * latter case we would have to store key2 here */
  	struct gf128mul_64k *table;
  	/* stores:
  	 *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
  	 *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
  	 *  key2*{ 0,0,...1,1,1,1,1 }, etc
  	 * needed for optimized multiplication of incrementing values
  	 * with key2 */
  	be128 mulinc[128];
  };
  
  static inline void setbit128_bbe(void *b, int bit)
  {

  	__set_bit(bit ^ (0x80 -
  #ifdef __BIG_ENDIAN
  			 BITS_PER_LONG
  #else
  			 BITS_PER_BYTE
  #endif
  			), b);

  }
  
  static int setkey(struct crypto_tfm *parent, const u8 *key,
  		  unsigned int keylen)
  {
  	struct priv *ctx = crypto_tfm_ctx(parent);
  	struct crypto_cipher *child = ctx->child;
  	int err, i;
  	be128 tmp = { 0 };
  	int bsize = crypto_cipher_blocksize(child);
  
  	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  				       CRYPTO_TFM_REQ_MASK);
  	if ((err = crypto_cipher_setkey(child, key, keylen - bsize)))
  		return err;
  	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  				     CRYPTO_TFM_RES_MASK);
  
  	if (ctx->table)
  		gf128mul_free_64k(ctx->table);
  
  	/* initialize multiplication table for Key2 */
  	ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize));
  	if (!ctx->table)
  		return -ENOMEM;
  
  	/* initialize optimization table */
  	for (i = 0; i < 128; i++) {
  		setbit128_bbe(&tmp, i);
  		ctx->mulinc[i] = tmp;
  		gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  	}
  
  	return 0;
  }
  
  struct sinfo {
  	be128 t;
  	struct crypto_tfm *tfm;
  	void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
  };
  
  static inline void inc(be128 *iv)
  {

  	be64_add_cpu(&iv->b, 1);
  	if (!iv->b)
  		be64_add_cpu(&iv->a, 1);

  }

  static inline void lrw_round(struct sinfo *s, void *dst, const void *src)

  {
  	be128_xor(dst, &s->t, src);		/* PP <- T xor P */
  	s->fn(s->tfm, dst, dst);		/* CC <- E(Key2,PP) */
  	be128_xor(dst, dst, &s->t);		/* C <- T xor CC */
  }
  
  /* this returns the number of consequative 1 bits starting
   * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
  static inline int get_index128(be128 *block)
  {
  	int x;
  	__be32 *p = (__be32 *) block;
  
  	for (p += 3, x = 0; x < 128; p--, x += 32) {
  		u32 val = be32_to_cpup(p);
  
  		if (!~val)
  			continue;
  
  		return x + ffz(val);
  	}
  
  	return x;
  }
  
  static int crypt(struct blkcipher_desc *d,
  		 struct blkcipher_walk *w, struct priv *ctx,
  		 void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
  {
  	int err;
  	unsigned int avail;
  	const int bs = crypto_cipher_blocksize(ctx->child);
  	struct sinfo s = {
  		.tfm = crypto_cipher_tfm(ctx->child),
  		.fn = fn
  	};
  	be128 *iv;
  	u8 *wsrc;
  	u8 *wdst;
  
  	err = blkcipher_walk_virt(d, w);
  	if (!(avail = w->nbytes))
  		return err;
  
  	wsrc = w->src.virt.addr;
  	wdst = w->dst.virt.addr;
  
  	/* calculate first value of T */
  	iv = (be128 *)w->iv;
  	s.t = *iv;
  
  	/* T <- I*Key2 */
  	gf128mul_64k_bbe(&s.t, ctx->table);
  
  	goto first;
  
  	for (;;) {
  		do {
  			/* T <- I*Key2, using the optimization
  			 * discussed in the specification */
  			be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
  			inc(iv);
  
  first:

  			lrw_round(&s, wdst, wsrc);

  
  			wsrc += bs;
  			wdst += bs;
  		} while ((avail -= bs) >= bs);
  
  		err = blkcipher_walk_done(d, w, avail);
  		if (!(avail = w->nbytes))
  			break;
  
  		wsrc = w->src.virt.addr;
  		wdst = w->dst.virt.addr;
  	}
  
  	return err;
  }
  
  static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
  		   struct scatterlist *src, unsigned int nbytes)
  {
  	struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
  	struct blkcipher_walk w;
  
  	blkcipher_walk_init(&w, dst, src, nbytes);
  	return crypt(desc, &w, ctx,
  		     crypto_cipher_alg(ctx->child)->cia_encrypt);
  }
  
  static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
  		   struct scatterlist *src, unsigned int nbytes)
  {
  	struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
  	struct blkcipher_walk w;
  
  	blkcipher_walk_init(&w, dst, src, nbytes);
  	return crypt(desc, &w, ctx,
  		     crypto_cipher_alg(ctx->child)->cia_decrypt);
  }
  
  static int init_tfm(struct crypto_tfm *tfm)
  {

  	struct crypto_cipher *cipher;

  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
  	struct priv *ctx = crypto_tfm_ctx(tfm);
  	u32 *flags = &tfm->crt_flags;

  	cipher = crypto_spawn_cipher(spawn);
  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);

  	if (crypto_cipher_blocksize(cipher) != 16) {

  		*flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
  		return -EINVAL;
  	}

  	ctx->child = cipher;

  	return 0;
  }
  
  static void exit_tfm(struct crypto_tfm *tfm)
  {
  	struct priv *ctx = crypto_tfm_ctx(tfm);
  	if (ctx->table)
  		gf128mul_free_64k(ctx->table);
  	crypto_free_cipher(ctx->child);
  }

  static struct crypto_instance *alloc(struct rtattr **tb)

  {
  	struct crypto_instance *inst;
  	struct crypto_alg *alg;

  	int err;
  
  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
  	if (err)
  		return ERR_PTR(err);

  	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
  				  CRYPTO_ALG_TYPE_MASK);

  	if (IS_ERR(alg))

  		return ERR_CAST(alg);

  
  	inst = crypto_alloc_instance("lrw", alg);
  	if (IS_ERR(inst))
  		goto out_put_alg;
  
  	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
  	inst->alg.cra_priority = alg->cra_priority;
  	inst->alg.cra_blocksize = alg->cra_blocksize;
  
  	if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
  	else inst->alg.cra_alignmask = alg->cra_alignmask;
  	inst->alg.cra_type = &crypto_blkcipher_type;
  
  	if (!(alg->cra_blocksize % 4))
  		inst->alg.cra_alignmask |= 3;
  	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
  	inst->alg.cra_blkcipher.min_keysize =
  		alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
  	inst->alg.cra_blkcipher.max_keysize =
  		alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
  
  	inst->alg.cra_ctxsize = sizeof(struct priv);
  
  	inst->alg.cra_init = init_tfm;
  	inst->alg.cra_exit = exit_tfm;
  
  	inst->alg.cra_blkcipher.setkey = setkey;
  	inst->alg.cra_blkcipher.encrypt = encrypt;
  	inst->alg.cra_blkcipher.decrypt = decrypt;
  
  out_put_alg:
  	crypto_mod_put(alg);
  	return inst;
  }
  
  static void free(struct crypto_instance *inst)
  {
  	crypto_drop_spawn(crypto_instance_ctx(inst));
  	kfree(inst);
  }
  
  static struct crypto_template crypto_tmpl = {
  	.name = "lrw",
  	.alloc = alloc,
  	.free = free,
  	.module = THIS_MODULE,
  };
  
  static int __init crypto_module_init(void)
  {
  	return crypto_register_template(&crypto_tmpl);
  }
  
  static void __exit crypto_module_exit(void)
  {
  	crypto_unregister_template(&crypto_tmpl);
  }
  
  module_init(crypto_module_init);
  module_exit(crypto_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("LRW block cipher mode");